Detecting apparatus for strands



Nov. 29, 1966 Filed May ll, 1964 G. DORNBERGER DETECTING APPARATUS FOR STRANDS 6 Sheets-Sheet l Nov. 29, 1966 G. DORNBERGER DETECTING APPARATUS FOR STRANDS 6 Sheets-Sheet 2 Filed May ll, 1964 N0V 29, 1966 G. DORNBERGER DETECTING APPARATUS FOR STRANDS 6 Sheets-Sheet 3 Filed May ll, 1964 Nov. 29, 1966 ca` DORNBERGER 3,287,887

DETECTING APPARATUS FOR STRANDS Filed May 11, 1964 6 Sheets-Sheet 4 NOV. 29, 1966 G, DQRNBERGER 3,287,887

DETECTING APPARATUS FOR STRANDS Filed May ll, 1964 6 Sheets-Sheet 5 Nov. 29, 1966 Filed May ll, 1964 G. DORNBERGER DETECTING APPARATUS FOR STRANDS 6 Sheets-5heet 6 GA 77/VG PULSES DE TEC 70? WFEAD FPFSEA/T United States Patent 3,287,887 DETECTING APPARATUS FOR STRANDS Georg Dornberger, Murray Hill, NJ., assgnor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed May 11, 1964, Ser. No. 366,407 15 Claims. (Cl. 57-19) This invention relates to detecting apparatus and particularly to apparatus for detecting the presence or absence of a strand such as when a binder thread is applied about a group of wire in the manufacture of communications cable.

In the manufacture of exchange area cable it is necessary to bind the individual conductors into wire groups or units for purposes of identification to facilitate making connections thereto. The binding operation is performed in a conventional multi-unit binder of the type disclosed in patent 2,944,378 to C. H, Crosby et al. which ordinarily includes about seven binder heads, each of which binds a separate wire unit with a fine nylon or textile thread. The bound units are formed together into a cable core and advanced through a binding head which wraps a binder about the moving core in a helical configuration. The bound core is fed to a twisting apparatus such as a strander ier where a twist is imparted to the core as the core is wound on a take-up device.

If a binder thread should break or the thread supply become depleted, a considerable length of a cable unit or core may pass through the particular head Without being bound. This produces a serious problem if connections must be made to an unbound portion of the cable which in some instances may comprise over a thousand pairs of Wire. Consequently,'it is desirable to immediately detect the absence of a thread at any one of a plurality of binder head positions and stop the binding operation.

One prior art device for detecting thread breaks involves a mercury switch having a feeler riding on the thread being fed to the cable unit. Whenever a break occurs, the feeler drops, activating the mercury switch which signals a timing relay to stop the binder drive. An important disadvantage of this method is that the tension applied to the thread by the feeler is one cause of the very breaks the device is designed to detect.

Another prior art detector includes an A.C. generator having its rotor connected to the thread supply spool and its stator' connected to the binding head. As the thread is drawn of, the spool being of either larger or smaller diameter rotates at a different speed than the head thereby producing an A.C. signal related to the speed differential. The signal is present as long as the thread is being payed off the spool, but if the thread should break, the spool which is mounted within the head comes to the same speed as the head, eliminating the speed differential between stator and rotor which generated the signal. The signal failure is then used to turn off the binder. One disadvantage of this detector is its inability to provide a rapid positive indication of thread breakage.

A further prior art detector employs a phototransistor mounted within a rotating head to sense the presence of a thread as it enters or leaves the head. The phototransistor is connected to a transmitter which emits a signal as long as a thread is being detected. A receiver mounted on a stationary guard closes a switch to turn off the binder when the signal fails indicating a thread break. The transmitter on each head is tuned to a different frequency to lessen interference from the other heads and to permit positive identification of the particular inoperative binder head. Nevertheless, the possibility of frequency interference still exists and may provide faulty indications. Also the thread tends to Whip near the head ICC and thus might not be in front of the phototransistor to provide an indication of thread presence and remounting of the detectors is required if the thread is to be wound in the opposite direction. v

The detecting apparatus of the present invention possesses numerous advantages over the aforementioned prior art detectors. The apparatus may be used in one embodiment to detect the presence of two threads, positioned 18() degrees apart, at a high-speed binder head despite relatively wide variations in thread position which make it difficult to detect the threads on a time basis. The apparatus will detect, in this instance, if either one or both threads break. The detector provides an instantaneous signal when a thread breaks without the possibility of interference which may occur when a different frequency is used for each head in a speed-differential type generator detector and without the delayed response or intermittent tension placed on the thread by conventional electro-mechanical detectors.

Accordingly, an object of this invention is to detect the presence of a thread being fed from a rotating binding head despite deviations from a normal thread position.

Another object of this invention is to sense the presence of a flamentary material rotating at high speed about a fixed axis.

Another object of this invention is to detect one or more threads being fed from a wire binding head which rotates within a wide speed range.

A further object of this invention is a rapid functioning gating circuit switching between a high and low input impedance condition.

A more specific object of this invention is to detect the presence of one or more threads which may vary from a normal position at each rotating binder head of a multi-unit binder and provide a signal to stop the binding operation if a thread should break.

The invention, in its broader aspects, comprises a thread or strand break detector for a cable binding operation including means for feeding a strand and detecting means synchronized with the strand feeding means and periodically operable to sense the presence or absence of the strand in a time slot variable with the speed of the feeding means. If a thread is absent, means responsive to the operation of the detecting means stop the operation of the feeding means.

In general, the detecting apparatus embodied herein provides a means for preventing runs of unbound cable units or cores by detecting broken binder threads and thereupon stopping the operation of the cable line until the trouble has been corrected. As a binder head rotates within the broad speed range of 5()y to 5000` r.p.m., a phototransistor gate circuit mounted on a stationary guard is intermittently operated by changes in the light reflected from the rotating head. In effect, the detector provides a time slot which is synchronized with the binder head and Varies in width or time duration with the speed of rotation of the binder head. One or more phototransistor detecting circuits, depending on the number of threads being detected, sense a designated binder thread in a predetermined sequence as the head rotates and supply a signal through the phototransistor gate. When no threads are broken, the gated outputs from the detector circuits operate a relay controlling the binder head drive. As long as the detector circuits provide a continuous signal the relay remains operated but if a thread breaks the relay is released and stops the binder head. The apparatus can be used with a single binder thread by inactivating the gate circuit or if several binder threads are required additional channels may be readily added to the circuit. A feature of the circuit is its ability to detect the presence of threads despite variations in thread position of up to in the case of each of two threads.

The gate signal from the phototransistor gate circuit is amplied, squared and fed to a first transistorized driver which functions as an A.C. switch to pass signals in a predetermined sequence from one or more detecting circuits to a ip-flop circuit. The thread detecting circuits each comprise a phototransistor, alinear amplifier and a squaring amplifier which sense a designated binder thread as the head rotates. When the required threads are present, i.e. no threads are broken, the outputs from the squaring amplifiers of the detecting circuits are alternately gated to a second driver through the flip-Hop circuit and a one-shot multi-vibrator. The second driver is coupled to a relay control circuit for the binder which holds in as long as pulses are supplied from the detecting circuits. If a thread breaks or is not present because the supply is exhausted, the dip-flop circuit is not activated by pulses from the detecting' channels and the motor control relay circuit drops out stopping the binding operation.

These and other objects and advantages of the present invention will be apparent from the following detailed description when considered in conjunction with the following drawings, wherein:

FIG. l is a block diagram illustrating the connection and association of the more important interacting circuits comprising the detecting apparatus of the subject invention;

FIG. 2 illustrates a circuit arrangement for detecting more than two binder threads;

FIGS. 3 and 4 illustrate the various circuits of FIG. l in greater detail;

FIG. 5 shows the arrangement of FIGS. 3 and 4;

FIG. 6 shows an end view of the binder with the detecting apparatus mounted thereon;

FIG. 7 shows a side view of the detecting apparatus taken along the line 7 7 of FIG. 6;

FIG. 8 is a view taken along the line 8 8 of FIG. 7;

FIG. 9 is an expanded isometric View illustrating the detecting apparatus of the present invention; and

FIGS. 10-101' illustrate various wave forms at selected circuit positions within the apparatus.

As disclosed in Patent 2,944,378 to C. H. C-rosby et al., a plurality of binder heads 65 of the type shown in FIGS. 6-9 are mounted on a multi-unit binder 60 and rotate independently of one another clockwise or counterclockwise depending on the wrapping mode at speeds up to 5G00 revolutions per minute. In the meantime, cable units 70 are being drawn through the center arbor 66 of each head 65 at speeds up to 600 feet per minute. One or more tine nylon or textile threads 40, which may range from .003 to .005 inch in width are wrapped about the advancing cable units 70 or cable core (not shown) to bind the conductors 71 into predetermined groups. The threads 40 are drawn from spools 61 mounted on the arbor 66 through an aperture 62 in the rotating head 65. The box 59 appearing in FIGS. 7 and 9 merely represents well-known means for forming. the individual conductors 71 into a cable unit 7 0.

A gate circuit 10 packaged within a protective cover in a conventional manner is mounted on a stationary guard 64 and is intermittently operated by changes in the light relected from a particular rotating head 65. The gate interval may be computed mathematically for the conditions prevailing at a head 65 and a strip of reflective material or tape 68 of a length which is related to the gating time may be placed on the heads 65 in the light path from lamp 11. The reiiected light is sensed by a phototransistor 12 in the gate circuit 10 as will be described in a detailed discussion of the circuit.

The detector circuits 20 and 30 are mounted adjacent a head 65 on support 67 which is attached to frame 69 by screws 63 and positioned so that the light from transmitters 21 and 31 is detected by phototransistors 22 and 32 respectively within said circuits, see FIG. 6. The detectors 20 and 36 are precisely located at fixed angles to the head 65 so that the binder threads 40 cut the light beams in a ixed sequence for a positive indication that a thread is present. FIG. 9 shows an expanded view of the binding head 65 with the various light paths indicated by dotted lines. The present arrangement of detectors 20 and 30 is designed to detect a pair of threads 40 which are positioned approximately apart but which may vary within plus or minus 20 of their normal position at wrapping speeds of 50 to 5000 r.p.m.

With reference to FIG. l of the drawings, the invention in one embodiment comprises a gate circuit 10 and a pair of detector circuits or channels 20 and 30 which alternately sense a designated binder thread 40 which is being fed from a rotating head 65 and wrapped about an advancing cable unit 70 in a helical coniiguration. The gate circuit 16, the channels 20 and 30, and the parts of the apparatus comprise conventional transistorized circuits which are described in detail only where necessary to explain the present invention. The detectors 20 and 30 supply a signal through the gate circuit 10` to the relay control circuit 50 for the binder drive. The control relay 55 in the circuit 50 remains operated as long as a thread 40 is being sensed by the detectors 20 and 30 but when a thread 40 breaks, the relay 55 drops out interrupting the signal to motor control 56, stopping the binder 60 and operating an alarm. Although only two detector channels 20 and 30 are disclosed for purposes of illustration in FIG. l it is to be understood that the present detecting apparatus would function equally well to detect a plurality of binder threads 40 at each head 65 by merely providing additional detector channels and associated circuits as shown in FIG. 2. The apparatus can also be used to detect a single binder thread 40 by inactivating the gate 10 so that a continuous signal is provided when the channels 20 and 30 detect the presence of the rather fine binder thread 40.

The .gate circuit 10 includes a linear amplifier 13 which receives an intermittent signal from the phototransistor 12 representative of a predetermined gating interval and feeds the signal to a squaring amplifier 14 which shapes the wave form to provide positive on-oii signals. The various wave forms are approximately depicted in FIG. l while FIGS. 10a to 10j also illustrate selected wave forms which will be discussed in detail later on. A driver 15 is connected to the output of the sqnaring amplier 14 and functions as an A.C. switch to alternately feed signals from the detector circuits 29 and 30' to a successively coupled fiip-op circuit 16, a one-shot multivibrator 17 and a second driver 1-8.

The detector circuits 20 and 30 include phototransistors 22 and 32 each of which detect the presence of a designated binder thread 40 as the threads 40 cut the light from transmitters 21 and 31. The signals are stepped down in impedance matched transformers 23 and 33 coupled through capacitors 24 and 34 to linear amplifiers 25 and 35. The -outputs from the linear ampliiiers 25 and 35 are fed to respective squaring ampliers 26 -and 36 to obtain on-off signals which are sharper than the detected pulses for rapid switching operations.

The squaring amplifiers 26 and 36 are coupled to the iiip-tiop 16 in the gate circuit 10 to provide set and reset signals to the bistable circuit 16 during the variable gating interval. As the binder speed varies from a low start-up speed to a normal running speed, the gating interval automatically becomes shorter necessitating an extremely rapid switching arrangement since at high speeds both threads 40 will activate phototransistors 22 and 32 for periods of two microseconds. Accordingly, the driver 15 functions as a switch when the gate is open, connecting the capacitors 27 and 37 a-cross the inputs to the squaring amplifiers 26 an-d 36, respectively. The resistance of driver 15 and either capacitor 27 or 37, both of which are rated at 50 micro-farads, 15 volts D.C. in the illustrated embodiment, are equivalent to a pair of impedances and do not affect the D.C. signal to the amplifiers 26 and 36 and 25 and 35 because of the presence of the capacitors. If the impedance connected to an amplifier inp-ut is low, the signal will pass to ground through the capacitor 27 or 37 but if the impedance is high, a condition which occurs during the gate interval, the signal passes to the particular squaring amplifier 26 or 36. Transistor 52 is turned off during the high impedance portion of the cycle by the gating pulse but operates to ground during the low impedance portion to block the particular iiip-op input. By switching the driver resistance into the detector circuits 20` and 30 in response to a signal from phototransistor 12, it is possible to rapidly sample the output signals from both detectors 20 and 30 during the extremely short time the gate 10 is open. This switching arrangement does not change the D.C. detector signal levels and is very fast in operation.

The detector outputs are gated to a ip-flop circuit 16 which iii-ps back and forth in response to the square wave signals from the detector channels 20 and 30. The flipflop output is fed to a one-shot multi-vibrator 17 which triggers for a fixed time interval every time it receives a pulse. While the length of the multi-vibrator output pulses is substantially constant, the interval between the input pulses varies in relation to the binder speed and gating interval. Consequently, the one-shot circuit 17 maintains the relay 55 ope-rational over a wide speed range by providing a relatively stable output. The oneshot circuit 17 activates a driver 18 which provides a power outp-ut to maintain relay 55 in the binder control circuit in its operated condition. Capacitor 51 is connected across relay 55 to provide storage for continued binder operation particularly during pulse drops at low speed.

If a thread breaks, no signal is supplied over the particular detector circuit 20 or 30 and the iiip-ilop does not receive alternate set and reset signals. Consequently, the Hip-flop circuit 16 remains in one condition and fails to activate the one-shot circuit 17. No output is supplied from the driver 1S and the relay 55 drops out stopping the binder drive and sounding an alarm. The relay 55 is selected so that it remains operated when the binder is rotating at a minimum speed such as 5 O r.p.m. but drops out below that value.

With particular reference to FIGS. a-10]', FIG. 10a shows the approximate wave form of the-gating pulses generated by phototransistor 12 during the interval when light from source 11 is reiiected from strip 68 on the rotating binding head 65. FIGS. 10b and 10c` depict the detector lpulses generated when threads 40 designated as thread-1 and thread-2 respectively intercept the light paths of a corresponding phototransistor 22 or 32. FIG. 10d illustrates the discontinuance of detector pulses from phototransistor 32 if a thread-2 should break.

FIG. 1()c shows the shaped gating pulses which are fed to the input of driver 15 from squaring amplifier 14 while FIGS. lOf and 10g illustrate, respectively, the squared detector outputs of amplifiers 26 and 36. The detector pulses of FIGS. lOf and 10g are fed to the flipop circuit 16 during the interval that the driver 15 is operated by the gating pulses. The driver 15 functions as a switch alternately grounding the detector signal from channels 20 and 30 and permitting the flip-flop circuit to be operated in the bistable manner shown in FIG. 10i. As long as the flip-flop 16 is operated the binder control 50 remains operative. If a thread should break as shown in FIG. 10]', the binder 60 would be shut down by the control circuit 50.

Power for the circuit operation is supplied by the conventional power source 45 which-is connected as shown in FIGS. 1 and 2. While the invention has been described with reference to a pair of binder threads 40, manifestly the apparatus could be used to detect any convenient number of threads by merely adding additional channels similar to circuits 20 and 30 and la series of flip-flop circuits and adjusting the gate circuit 10 accord- 6 ingly. FIG. 2 illustrates an arrangement for detecting four threads 40 at a single binder head 65 wherein the detector pulses are fed to the gate 10 through flip-flops 16a or 1Gb and flip-op 16C. The apparatus can also be used to detect a single binder thread 40` by closing switch 19 which turns the gate 10 on permanently so that the signals from the detectors 20 and 30 are continuously fed through the gate circuit to the motor control circuit 50. As a further advantage, the disclosed detector can be used with either clockwise or counterclockwise binding.

Since the individual circuits represented by the blocks of FIGS. l and 2 are conventional in design, no detailed description of these circuits has been attempted. Nevertheless, detailed circuits for a typical embodiment of the invention have been shown in FIGS. 3 and 4, the oper-ation of which is apparent in the `light of the foregoing description.

The invention, of course, is not limited to binder heads. It could in general be applied to different types of strand feeding, for instance, a tap-ping head for applying tape to wire or a wire core.

It is to be understood that the .above-described arrangements yare simple illustrative examples of the application of the principles of the invention. Numerous other arrangements may be readily devised by Ithose skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. An apparatus for detecting strand material during a strand feeding operation comprising:

means for feeding a strand,

detecting means `synchronized with the strand feed-ing means and periodically operable to sense the presence or absence of the strand in -a time slot variable with the speed of the feeding means, and

means responsive to the operation of the detecting means for stopping the operation of the feeding means when the strand is absent.

2. An apparatus in accordance with claim 1 wherein the detecting means comprises:

light sensitive means,

3. An apparatus in accordance with claim 1 wherein the means responsive to the oper-ation of the detecting means comprises:

circuit means operable so long as a strand is detected by the detecting means, `said circuit means becoming effective to stop the operation of the feeding means when the strand is absent.

4. A thread break detector for a cable binder comprising:

a gate circuit for intermittently passing `a signal during a variable gate interval related to the rotational binder speed,

a plurality of detector circuits associ-ated with the gate circuit, each of said detector circuits being designed to sense `the presence of a designated thread in -a predetermined sequence during the gate interval and feed a signal through the gate circuit, and

means responsive to the gated detector signal to stop the operation of the binder in the absence of a thread interrrupting the signal normally received from the detectors.

5. A detector in accordance with claim 4 wherein the gate circuit compri-ses:

a pihototransistor adapted to be operated by light for time intervals dependent on the speed of rotation of the binder to generate a gating signal, 1 amplifying means coupled to the phototr-ansistor for amplifying and yshaping the gating signal, and

a driver circuit coupled to the output of the amplifying means and to the detector outputs and operable by means of the gating signal to sample the detector circuits in a predetermined sequence during -a gating interval and feed the detector signals to the 7 means responsive thereto to control the operation of the binder.

6. A detector in accordance with claim 4 wherein the detector circuits each comprise:

light-sensitive detecting means for generating a pulse when a designated thread is present, and

amplify-ing means coupled to the light-sensitive detecting means for feeding lan amplified pulse to the gate circuit during the gating interval to indicate the presence of the thread.

47. A thread break detector in accordance with claim 4 wherein the means responsive to the detector signal comprises:

a Hip-flop circuit coupled to the outputs of the plurality of detector circuits to operate upon receiving successive gated signal-s from the detector circuits,

a one-shot multi-vibrator connected to the llipdiop circuit to operate upon receiving a detector signal,

a drivercircuit connected to the one-shot multi-vibrator to provide a power output from the gate .as long as signals are received from the detector circuits, and

a relay circuit for controlling the binder operation, said circuit remaining operable so long as detector signals lare received but said circuit dropping out if a thread breaks and no signal is received.

8. An apparatus for detecting the presence of rotating lamen-tary material being applied about a moving cable unit comprising:

a rst detector circuit including light-sensitive detecting means mounted in a fixed position with reference to the cable unit axis for generating a pulse when the rotating iilamen-ta-ry material passes the detecting means,

a -second detector circuit adapted to be operated in a predetermined sequence in relation to the first detector, said second detector including light-sensitive detecting means mounted in a lixed position with reference to the cable unit axis for generating a pulse when the rotating lamentary material passes the detecting means,

means individual to each detector for shaping the generated pulse,

a flip-flop circuit coupled to the outputs of the detector circuit-s and operable by the shaped pulses generated by the detectors, and

means connected to the flip-op circuit responsive to the alternating pulses therefrom to permit continued movement of the cable unit so long as pulses are received from the detectors indicating the presence of ilamentary material.

9. An apparatus for detecting thread breakage on a cable binder, wherein at least two threads are fed from a rotating binder head about an advancing wire grouping, comprising:

individual means for detecting the presence of a particular thread during eac-h rotation of the binder head,

means for rapidly .switching between the detecting means during a predetermined time interval to determine the presence of each thread, and

means operable by the detecting means during the switching interval to permit continued operation of the binder head if all the threads 'are present.

10. An apparatus for detecting the presence of a plurality of rotating binder threads bei-ng applied by a binder apparatus about a wire grouping which moves through a cable manufacturing line -at varying speeds comprisga plurality of detector circuits each adapted to sense the presence of a designated binder thread and produce a pulse during each revolution, of the thread,

a gate circuit intermittently oper-able by the binder apparatus to open a circuit path for the detector pulses, and

circuit means coupled to the gate circuit to receive a 'series of detector pulses when the gate is open indicating that no threads are broken, said means controlling the operation of the binder apparat-us.

11. An .apparatus in accordance with claim 16 Wherein the detector circuits each comprise:

.a phototransistor mounted in a tixed position on the bi-nder apparatus to be activated by a designated binder thread when the gate circuit is open,

a linear amplier connected to the phototransistor to amplify the detector pulses, and

a squaring amplier connected to the output of the linear ampli-lier to square the detector pulses.

12. An apparatus in accordance Wit-h claim 10 where- -in the g-ate circuit comprises:

pulse generating means operable for a time interval varying with the binder speed,

a linear amplifier connected to the pulse generating means to .amplify the gating pulses therefrom,

a squaring amplifier connected to the output of the linear amplier to square the gating pulses, and

a driver connected to the squaring amplier and coupled to the detector circuits to be operated by the gating signals to open a circuit path to a predetermined seuence of detector signals related to the threads being detected.

13. An apparatus in accordance with claim 10 wherein the circuit means coupled to the gate circuit cornprises:

a series of flip-flop circuits connected such that a single iiip-op circuit is coupled .to the outputs of each two detector circuits to provide an alternate signal when the gate is open and the outputs from each two flip-op circuits :are fed to another flip-dop circuit the succession of ip-op circuits continuing until the output from the series of circuits is fed from la single flip-flop circuit,

a oneshot multi-vibrator connected to the output from the series of ip-ozp circuits and operable upon receiving a signal therefrom,

a driver circuit connected to the output of the oneshot multi-vibrator and operable thereby to provide a power output, and

a control circuit for the binder connected to the driver circuit output, said control circuit lremaining operated so long as detector pulses are supplied indicating that the binder threads are present.

14. An apparatus for detecting the presence of one or more strands being wrapped about a conductor grouping in a helical configuration by a rotating binder head comprising:

separate means for detecting the presence of each strand during a rotation of the binder head and generating a pulse,

a gate circuit coupled to the detecting means, having a gating interval related to the binder speed to open -a circuit p-ath to the generated pulses during a portion of each revolution of the binder head,

means for rapidly switching from one detecting means to another in a predetermined sequence, said means comprising individual grounded capacitors and a variable resistance coupled to each detecting means to permit passage of pulses by variations in the coupled resistance during the gating interval, and

means coupled to the output of the switching means and operable thereby to permit continued operation of the binder head if pulses are being received from the detecting means indicating that all Ithe strands are present.

15. A gating circuit to permit passage of signals during a predetermined time interval comprising:

a circuit path for passage of signals,

a capacitor connected to the circuit path,

circuit means actuable during -a predetermined gate interval, and

a driver circuit having an input connected to the circuit means and operable thereby and having a first output connected lto the capacitance and a second output connected to ground to provide 'a high impedance path blocking signals from the circuit path to the driver during a gate interval when the driver is inoperative but permitting the passage of signals along the circuit path, said driver becoming oper-ative at the end of a lgate interval to present a low impedance path to ground shorting the circuit path to ground.

References Cited by the Examiner UNITED STATES PATENTS 2,148,665l 2/1939' WOlfe 57-81 X 5 2,770,091 11/ 1956 Frankel 57-81 3,114,233 12/1963 Guti 5,7-81 3,158,852 11/1964 Schacher 57--81 X FRANK J. COHEN, Primary Examiner. 10 D. E. WATKINS, Assistant Examiner. 

1. AN APPARATUS FOR DETECTING STRAND MATERIAL DURING A STRAND FEEDING OPERATION COMPRISING: MEANS FOR FEEDING A STRAND, DETECTING MEANS SYNCHRONIZED WITH THE STRAND FEEDING MEANS AND PERIODICALLY OPERABLE TO SENSE THE PRESSENCE OR ABSENCE OF THE STRAND IN A TIME SLOT VARIABLE WITH THE SPEED OF THE FEEDING MEANS, AND MEANS RESPONSIVE TO THE OPERATION OF THE DETECTING MEANS FOR STOPPING THE OPERATION OF THE FEEDING MEANS WHEN THE STRAND IS ABSENT. 